The latest version of Ultrasn0w (v1.2) can not unlock iPhone 3GS/3G baseband 05.14.xx or 05.15.xx. To unlock these basebands, first you must use PwnageTool 4.1.3 to update your baseband to 06.15.00 and then you can unlock your iPhone with Ultrasn0w 1.2. This guide will explain you how you can use PwnageTool 4.1.3 to upgrade your iPhone 3G/3GS baseband to 06.15.00.Update: Instead of using PwnageTool 4.1.3, now you can use Redsn0w 0.9.6b5 to update iPhone 3G/3GS baseband from 05.14/05.15 to 06.15.00. It don't require you to download iPad iOS 3.2.2 IPSW plus its available for both Windows and Mac OS X users.

Before you may proceed, please read this official disclaimer by iPhone Dev-Team:

WARNING - YOU DO THIS AT YOUR OWN RISK!PLEASE UNDERSTAND THE CONSEQUENCES OF UPDATING TO 06.15

There is no way to come back down from 06.15, and there's no hiding the baseband version from Apple. You'll be voiding your warranty in a very obvious way.

If some future baseband comes out with a critical fix, you won't be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn't update to it if you wanted to keep your unlock anyway).

Starting with FW 4.2.1 if you have 06.15 on your iPhone you won't ever be able to restore to stock firmware (it will fail). You'll need to only restore to custom IPSWs (then again, if you're unlocker you should already be doing that).

Once done, connect your iPhone to your Mac through USB cable and hold down the Power and Home button simultaneously for 10 seconds, after 10 seconds release the Power button but continue holding the Home button until PwnageTool detects your iPhone in DFU mode.

Once done, you will see iOS 4.1 custom IPSW file for your iPhone on your desktop.

How to Restore iOS 4.1 Custom IPSW Through iTunes:

Once you have successfully created the iOS 4.1 custom IPSW through PwnageTool and your iPhone is in DFU mode, launch iTunes and click on the name of the device from the side panel to view the summary page.Now you will see two buttons, Check for Updates and Restore. Hold down the ALT key (SHIFT for Windows) and click on the Restore button to browse for iOS 4.1 custom IPSW file you just created with PwnageTool 4.1.3.

Now wait until iTunes restores the custom cooked iOS 4.1 IPSW on your iPhone. If you see iTunes error 1004 or 1015 during the restore, don't panic because the firmware restore on your device is now complete. All you need is to kick your device out of recovery mode by using RecBoot or TinyUmbrella software.

Unlock iPhone 3GS/3G Baseband 06.15.00 With Ultrasn0w 1.2:

Once your iPhone has been jailbroken on iOS 4.1 by using the above procedure, your iPhone baseband should be 06.15.00. You can now use Ultrasn0w 1.2 to unlock your iPhone. Now you can use step-by-step guide here to unlock iPhone 3G/3GS baseband 06.15.00 on iOS 4.1.

Thanks a Million!! I dont know that much about iphones, but your directions were ON POINT!! And the easiest for me to follow…(out of all the ones I looked up!) I’m so excited that my iphone is unlocked and works! Could have never done it without your help…So big UPz to you Wolverine =)